1. Field of the Invention
The present invention relates to an apparatus for laterally retaining and guiding a ski boot on a cross-country ski. The boot is attached at its front end to the ski in such a manner that the heel is free to be displaced at least vertically. The invention also relates to such a boot and a cross-country ski that are made in such a manner as to assure this lateral guidance and retention of the boot on the ski.
2. Description of Pertinent Information
Devices for laterally retaining and guiding a cross-country ski boot on a ski are known. Many of these devices comprise a longitudinally extending guidance or retention rib which cooperates with a groove of the same shape provided in the sole of the boot. This rib laterally retains and guides the boot during the unfolding of the boot, that is, when the boot is applied flat on the ski. This guidance or centering rib extends longitudinally along the length of the plantar zone of the boot. Such a retention and guidance device is described in French Pat. No. 2,443,853 of Assignee.
In all such previously developed retention devices the guidance and retention rib has a cross-sectional configuration which is symmetrical with respect to a vertical and longitudinal plane. In other words, the two lateral and longitudinal surfaces of the rib have the same average gradient with respect to the horizontal surface of the ski. However, this gradient, or in other words, the angle that the lateral surface forms with the horizontal surface of the ski must be sufficiently "steep" so that the retention rib comprises an effective lateral retention abutment for the boot when the boot exerts an outwardly, downwardly, and rearwardly directed force on the ski. Such a force is generated when the skier practices what is commonly known as the "skater half-step" during skiing. In this cross-country technique only one of the skis, for example the left ski, is maintained in the longitudinal track of the slope. The skier then pushes in a repetitive manner on his other ski (the right ski in this example) on the side of the slope. The right ski forms with the left ski at the moment of pushing on the snow a sharp angle open toward the front. However, although this increase in the gradient of the lateral inclined surface of the retention rib permits an excellent lateral retention of the boot, it also diminishes to some extent, the ability of the rib to recenter the boot. Therefore, there is a need for a compromise which will simultaneously assure an effective lateral retention of the boot, and a better recentering of the boot on the ski and a better removal of snow which can lodge itself under the sole of the boot.